In general, a light emitting device comprises a package body with a recess and a light emitting diode mounted within the recess of the package body. The light emitting diode has advantages in that it has a smaller size, a longer life span and lower power consumption as compared with an incandescent bulb, a fluorescent lamp and a discharge light source.
An encapsulant is used to protect a light emitting diode from external environment, i.e. moisture. The encapsulant covers the light emitting diode and bonding wires to protect them from the external environment. Thus, the light emitting diode is mounted within the package body and then covered with the encapsulant to complete a light emitting diode package.
Hitherto, an epoxy resin has been widely employed as an encapsulant. However, since the epoxy resin causes the disconnection of the bonding wire due to its relatively large hardness and absorbs short wavelength visible light, there are problems of reduction in light flux or yellowing. In order to solve these problems, silicone has been recently used as an encapsulant. It is also known that due to small hardness and strong restoring force of a silicone encapsulant, the occurrence of disconnection of a bonding wire is reduced and the yellowing tendency is not exhibited even though it is used for a long time.
Furthermore, a variety of lenses are attached to an encapsulant to adjust the viewing angle or emission direction of light. However, a prior art for attaching a lens to an encapsulant may lower light extraction efficiency due to poor bonding or refractive index difference between encapsulant and lens, or the like.
Further, in a case where a light emitting diode is mounted within a recess of a package body, it is difficult to predict the path of light emitted to the outside due to light reflection produced on a sidewall of the recess or on an interface between an encapsulant and a lens. Since it is difficult to predict the path of light emitted from a light emitting diode to be incident onto a lens, it is difficult to design a lens capable of precisely adjusting a required viewing angle or emission direction of light.
An object of the present invention is to provide a light emitting device capable of preventing reduction in light extraction efficiency due to an interface between encapsulant and lens.
Another object of the present invention is to provide a light emitting device wherein the path of light emitted from a light emitting diode to be incident onto a lens can be simplified to easily design a lens.
To achieve the aforementioned objects of the present invention, the invention provides a light emitting device with a silicone lens. The light emitting device according to an embodiment of the invention comprises a heat sink. A package body surrounds at least a portion of the heat sink, and a light emitting diode is mounted on the heat sink. Meanwhile, the light emitting diode is covered with a silicone lens molded on the package body. The molded silicone lens can be employed to prevent reduction in light extraction efficiency due to poor bonding between a conventional lens and an encapsulant.
Hereinafter, the light emitting diode means a light emitting diode die or light emitting diode chip. The light emitting diode may be composed of a single diode or a plurality of diodes.
Meanwhile, a top surface of the light emitting diode is positioned at least above a top surface of the package body. In this case, since it is possible to prevent light emitted from the light emitting diode from being reflected on an inner wall of the package body, the path of light incident on the silicone lens can be easily predicted, and thus, the design of lens can also be easily made. The position of the top surface of the light emitting diode is set in accordance with the height of the top surface of the heat sink. The top surface of the heat sink is positioned near the top surface of the package body so that the top surface of the light emitting diode can be positioned at least above the top surface of the package body. The top surface of the heat sink can be positioned in the same plane as or higher than that of the package body.
A silicone encapsulant may be interposed between the silicone lens and the light emitting diode to cover the light emitting diode. Each of the encapsulant and the lens is made of a silicone material. Since the silicone lens is particularly molded on the encapsulant, the reduction in light extraction efficiency due to refractive index difference and poor bonding between lens and encapsulant can be prevented. Meanwhile, the silicone lens and/or silicone encapsulant may contain a phosphor capable of converting the wavelength of light emitted from the light emitting diode. Accordingly, a light emitting diode that generates a single wavelength can be employed to implement multicolored light, e.g. white light.
The silicone lens can be designed in various ways depending on the required viewing angle and/or emission direction of light. For example, the silicone lens may be a convex lens, a concave lens or the like, and may have a total internal reflection surface to emit light in a lateral direction.
According to the embodiment of the present invention, a light emitting device can be provided wherein a silicone lens molded on a package body is employed to prevent the reduction in light extraction efficiency due to poor interface between encapsulant and lens. Further, a light emitting device can be provided wherein the path of light emitted from a light emitting diode to be incident on a lens can be simplified to easily design the lens.